1. Field of the Invention
The present invention relates to poultry vaccines and, more particularly, to a novel method of delivering a protein to poultry involving spraying with a live avirulent derivative of an enteropathogenic bacterium.
2. Description of Related Art
Contamination of poultry meat and eggs by enterobacterial human pathogens, such as Salmonella spp. is a well known cause of illness in humans when such contaminated products are consumed. The contamination occurs predominantly during processing of carcasses after slaughter by contact with intestinal contents that contain high levels of such enterobacteria. The enterobacteria colonize the intestinal tract, but do not normally cause disease in the poultry. In order to reduce the contamination of food with enteropathogens it would thus be desirable to diminish the amount of human enteropathogenic bacteria present in the intestinal tracts of market-age broilers. Efforts to reduce this contamination have focused on improved sanitation during production and processing (Bailey, J. S., Poult. Sci., 72:1169-1173, 1993), but such techniques are time-consuming and expensive and are not totally effective in avoiding sporadic contamination. (See, e.g., Food Borne Disease Outlook Annual Summary, 1982; and Salmonella Surveillance Annual Survey 1992; both available from Center for Disease Control, U.S. Department of Health and Human Services, Atlanta, Ga.). Methods that depend upon sanitation during processing must be repeated frequently since processing equipment and personnel can be recontaminated by each contaminated fowl that is processed. Methods that depend upon sanitation during production require constant vigilance due to the high potential for contamination in the production environment. Therefore, a simple and inexpensive method to control enteropathogenic microbes in poultry during growth would be a key improvement in reducing carcass contamination during processing.
Promsopone et al., J. Food Protect., 61(2): 176-180, 1998, have reported that S. typhimurium colonization of the intestinal tracts of poultry can be reduced by administration of an avian-specific probiotic combined with S. typhimurium specific antibodies. Lactobacillus acidophilus, Streptococcus faecium and S. typhimurium-specific antibodies were administered by spraying the chicks at one day of age followed by oral administration via the drinking water from day 1 to day 3. The chicks were challenged by oral administration of S. typhiimiurium on day 1 and significantly reduced amounts of S. typhimurium were recovered from the cecum and colon following probiotic-treatment at 31, 38 and 43 days. Although administration of probiotic and antibodies as early as 1 day of age may have been important in reducing colonization of the intestine by S. typhimurium, it is not clear from this report whether the initial spray administration of probiotic and antibodies or the more commonly used oral administration in the drinking water on days 1-3 was responsible for decreasing S. typhimurium colonization.
Vaccines for use in preventing diseases in poultry have been reported and some of these vaccines are specific for Salmonella (See, e.g. U.S. Pat. Nos. 5,294,441, 5,389,368, 5,468,485 and 5,387,744). The methods for administration of vaccines in poultry vary, however, depending upon the target site of action of the active agent. In fact, it is commonly believed that the vaccination route should be tailored according to the preferential site of the microorganism for localization and replication. Thus, for Newcastle disease and infectious bronchitis viruses which multiply in the respiratory route, the vaccination methods of choice would be by eye drop into the eye, nasal passage and respiratory system of the chick or by the spray route. (Giambrone, World Poultry—Misset 13:19-23, 1997). Since many of the more important diseases of poultry occur in the respiratory tract, studies reporting on administration of spray vaccination for these diseases have used spray administration because an aerosol or spray is easily inhaled by the bird and thereby contacts the mucosal surfaces of the upper respiratory tract. Administration of vaccines for non-respiratory diseases, such as diseases of the tissues, circulatory system or gut, is usually by subcutaneous injection, or by oral administration, either by inoculation or by application in drinking water.
References disclosing the use of the spray administration of vaccines to poultry have almost exclusively been directed to immunizing against viral agents that invade through the upper respiratory tract such as, for example, to prevent Newcastle disease, avian encephalomyelitis, Marek's disease, laryngotracheitis, infectious bronchitis and the like. The reasons for this state of affairs are likely based on the commonly accepted knowledge that, in mammals, aerosol immunization has the potential to elicit both mucosal and systemic immunity, the balance between the two being manipulated by the aerodynamic particle size of the aerosol. Antigen delivered in aerosols with particle size >5 μm impinges on the mucosa of the upper respiratory tract, is taken up either directly, or delivered to the local lymphatic tissue and initiates mucosal immunity. Aerosols <5 μm deposit deep in the lung where antigen is taken up by lung-associated lymphoid tissue and transported by the draining lymphatics to the bloodstream and thus to the spleen, resulting in both a local and a systemic immune response. (See, Dertzbaugh, M. T., et al., Chap. 52, pp.839-849, at p. 846, in Mucosal Immnunology, 2nd Ed., P. L. Ogra et al., Eds., Academic Press, San Diego (1999)).
Bacterial vaccines, in particular live attenuated mutants derived from highly virulent bacterial parent strains, have also been used in poultry (Roland, K. et al., Efficacy of Salmonella typhimurium vaccine strains expressing Escherichia coli 078 lipopolysaccharide to protect against E. coli challenge in chickens, Abstract of a presentation at Conf. Of Res. Workers in Animal Diseases, Chicago, Ill., Nov. 10, 1997). Derivation of the attenuated mutant strain from a highly virulent parent increases the likelihood that the attenuated mutant will not only colonize the intestinal tract but also colonize the gut associated lymphoid tissue (GALT) and elicit protective immunity. (See, e.g., Curtiss III et al., in Colonization Control of Human Bacterial Enteropathogens in Poultry, Blankenship et al., eds, Academic Press, Inc., New York, 1991, 169-198). In contrast, bacteria that colonize the intestine but do not invade and colonize the GALT may not elicit an immune reaction. For example, studies in mice have revealed that lipopolysaccharide (LPS) O-antigen repeats on the surface of S. typhimurium are important not only to withstand nonspecific host defense mechanisms (Microbial Toxins, Vol. V, Roantree et al., eds., Academic Press, New York, 1971), but also for effective invasion through the mucin and glycocalyx covering the intestinal tract. As a consequence, rough mutants lacking LPS O antigens, when given orally, are unable to invade and colonize the GALT (See, e.g. Curtiss et al., 1991, supra).
Some references have reported on the administration of bacterial vaccines to poultry by oral or subcutaneous injection. For example, one commercial vaccine to prevent paratyphoid in pigeons comprises killed S. typhimurium administered by subcutaneous injection (Vetafarm Paratyphoid Vaccine, Vetafarm Pty. Ltd., Wagga Wagga, Australia). In addition, Curtiss et al, 1991, supra, report the use of an avirulent derivative of a pathogenic Salmonella as an orally administered vaccine in chicks.
Spray vaccination has also been reported for bacterial vaccines that cause respiratory diseases Hertman et al. report on oral and aerosol administration of a Pasteurella multocida vaccine to chickens and turkeys to prevent fowl cholera, which is a respiratory tract disease (U.S. Pat. No. 4,169,886). Ley et al. report on eye-drop and aerosol administration of a vaccine containing live Mycoplasma gallisepticum, which produces a respiratory tract disease (Ley et al., Avian Diseases 41:187-194, 1997). A commercially available vaccine recommends administration of a vaccine containing an avirulent strain of E. coli serotype O78 to immunize against the respiratory disease caused by the wild-type parent (see Product Bulletin for GARAVAX®-T, Schering-Plough Animal Health Corp., Omaha, Nebr.). The use of an aerosol administration for all of these vaccines would have been selected because the underlying disease for which the poultry were being vaccinated involved infection of the respiratory tract.
Another reference reported that a vaccine containing a strain of the nonpathogenic E. coli K-12 lacking O-antigen could be administered as an aerosol (U.S. Pat. No. 4,404,186). Nevertheless, the K-12 strain is a laboratory-adapted strain and is not an enteropathogen and because this microbe has no ability to invade and colonize the gut associated lymphoid tissue, it is likely that any immunity elicited by this vaccine would have been due to immunization through the respiratory route.
Localized spraying of bacterial vaccines such as by nasal spraying or ocular spraying had been suggested in some references (for example, see U.S. Pat. No. 5,294,441). Nevertheless, none of this earlier work suggested the use of whole body spray administration of enteropathogenic bacterial vaccines.
Therefore, while spray-administered vaccines have been reported to be useful in controlling respiratory diseases in poultry, whole-body spray administration has not been suggested for vaccines in poultry for the control of human pathogens that are often present in and transmitted by poultry, but which are not the causative agents for respiratory disease in poultry.
Modem commercial poultry practice sometimes requires the delivery of proteins to the birds, other than antigenic proteins for the purpose of eliciting an immune response. For example, growth factors, immunoregulatory proteins and peptides, and other biologically active proteins and peptides are often delivered to birds. The delivery of these proteins is most commonly done by inclusion in the feed or drinking water, but these methods are useless for newly hatched chicks, since they do not eat or drink for up to several days after hatching. In addition, the inclusion of labile proteins in drinking water or feed, can often result in the inactivation of a significant portion of the active molecules due to microbial activity, thermal degradation, or oxidation.
Accordingly, it would be desirable to provide a method that could be used to deliver selected proteins to domestic poultry in a manner that would be easy and inexpensive to administer under normal commercial poultry production conditions, and which would be effective for delivering the proteins to newly hatched chicks in an effective manner and without individual handling.